The use of polyesters as plasticizers for polyvinylchloride (PVC) homopolymers and copolymers is known. The use of these plasticizers has grown markedly in recent years due to their low volatility and resistance to migration. There are, however, certain disadvantages associated with the use of polyester plasticizers. The polyesters are not as efficient as simple ester plasticizers and large amounts are therefore required to achieve the same level of flexibility -- with resulting decrease in the mechanical properties of the resin. Also, the heretofore known polyesters adversely affect the low temperature properties of the final product as compared to the simple ester plasticizers.
It is an object of this invention to produce mixed-terminated polyesters capable of imparting flexibility and softness for PVC and other resinous materials. A further objective is to provide plasticizers having superior low temperature performance, low volatility and resistance to extraction.